Allow _redirects to be placed in root directory

[roschaefer]

This was easier to fix than expected. The fix should allow users to have their own _redirects file in the project root. If this file exists, it gets copied to build/ before adapter-netlify appends the catchall rule to it.

This behaviour is already documented, but currently broken.

How can I write an automated test for this adapter?

I did the following to test this manually:

1. Use yarn link "@sveltejs/kit" and yarn link "@sveltejs/adapter-netlify" in my application repository to point the two node modules to my modified versions.
2. Run svelte-kit build with a _redirects file in the project root.
3. Check if content of build/_redirects is expected.
4. Run svelte-kit build without a _redirects file in the project root.
5. Check if content of build/_redirects is expected.

Any guidance or help how to match the desired code quality to get this PR merged is appreciated.

close #1585

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[benmccann]

@kvn-shn @sw-yx @mikenikles as our resident Netlify users, can you guys reproduce this and are you okay with this change?

[kvn-shn]

I cannot reproduce this. Actually I wouldn't change it because I believe everything is working fine. There just seems to be a small misunderstanding, see #1585 (comment)

[swyxio]

ah yeah what kvn-shn said. it needs to be in the final directory that gets served by netlify, and for sveltekit that is the static folder, not project root.

[roschaefer]

Yes! 🎉 you're totally right. I'm going to close this as it's not needed.

[benmccann]

I would have expected it to be in the root directory, so without having looked at this much, this didn't seem like a bad change to me. Do we think static is the better place for it? If so, should we add some documentation about that?

[swyxio]

i do think its intuitive to be in the root for people who dont know how netlify works (and pretty self explanatory if you need to move the whole thing into a monorepo setup), but am hesitant to make a special rule that only works for sveltekit but not for anything else. i dont feel strongly about this one but we can always add some docs. did one #1596

[roschaefer]

I'm totally happy putting my _redirects in static/ and I suggest to keep everything as it is. The only thing that could be improved is documentation to save others from the same confusion. I offered to write some when I closed the referenced issue #1585 (comment) but @sw-yx already did in #1596.

So all is well.

[roschaefer]

OK, I'm happy with my own solution, too! 🤷‍♂️ Proud to be a Svelte-Kit code contributor now.